build(deps): bump slack-sdk from 3.18.2 to 3.18.3 in /.github/actions…

…/pr_notifier (envoyproxy#22999)

build(deps): bump slack-sdk in /.github/actions/pr_notifier

Bumps [slack-sdk](https://github.com/slackapi/python-slack-sdk) from 3.18.2 to 3.18.3.
- [Release notes](https://github.com/slackapi/python-slack-sdk/releases)
- [Changelog](https://github.com/slackapi/python-slack-sdk/blob/main/docs-v2/changelog.html)
- [Commits](slackapi/python-slack-sdk@v3.18.2...v3.18.3)

---
updated-dependencies:
- dependency-name: slack-sdk
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/actions/pr_notifier/requirements.txt

@@ -111,9 +111,9 @@ six==1.16.0 \
     --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
     --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
     # via pynacl
-slack-sdk==3.18.2 \
-    --hash=sha256:69befeadfbfc9238e85d0641c864cd12bfb162fbdf3e8f9eef30180f171ea675 \
-    --hash=sha256:d895fa191f2288d74cbbf20055be2f39c54397b3288c766fcd31e3f5828ef937
+slack-sdk==3.18.3 \
+    --hash=sha256:1bac09ed465bf9a0a120afce495b328969af7f032fe38cacbadace3dc1e49709 \
+    --hash=sha256:d28a661a7fde37c1763e594be19899a51e76ce7c480172c9cf22e217a72731c3
     # via -r requirements.in
 urllib3==1.26.6 \
     --hash=sha256:39fb8672126159acb139a7718dd10806104dec1e2f0f6c88aab05d17df10c8d4 \